With the advancement of communication technologies, the applications using communication technologies have also increased significantly, thus making the related products more diversified. Especially, consumers have more demands on advanced functions from communication applications, so that many communication applications with different designs and functions have been continuously appearing in the market, wherein the computer network products with wireless communication functions are the main streams recently. Moreover, with integrated circuit (IC) technologies getting matured, the size of product has been gradually developed toward smallness, thinness, shortness and lightness.
An antenna in the communication products is an element mainly used for radiating or receiving signals, and the antennas used in the current wireless products have to own the features of small size, excellent performance and low cost, so as to be broadly accepted and confirmed by the market. According to different operation requirements, the functions equipped in the communication products are not all the same, and thus there are many varieties of antenna designs used for radiating or receiving signals, wherein a patch antenna is quite commonly used. In order to obtain an antenna with high gain and broadband operation, the distance between the base board and the radiating metal plate can be increased for promoting the radiation efficiency and the operation bandwidth of the antenna. Generally, the features of antenna can be known by the parameters of operation frequency, radiation pattern, return loss, and antenna gain, etc. Hence, the design of patch antenna has to simultaneously consider the factors of appropriate distance between the base board and the radiating metal plate, and good antenna features.
On the other hand, the conventional dual-band antennas merely can cover a relatively small frequency range, and thus can be used in respective specific areas. For example, the frequency bands used in Japan, Europe and USA are all different, and thus different dual-band antennas have to be used in various areas.
However, it is very difficult for the conventional patch antenna, especially for the conventional dual-band patch antenna, to simultaneously have the feature of wide frequency range with the advantages of low cost, small size, high antenna gain, broad operation bandwidth and good radiation pattern, so that the applications of the conventional patch antenna are greatly limited.
Hence, there is an urgent need to develop a dual-band patch antenna for satisfactorily meeting the antenna requirements of wide frequency range, small size, high gain, wide broadband, simple design, low cost and small second harmonic, etc., thereby overcoming the disadvantages of the conventional patch antenna.